Re: [PATCH 01/19] compat ABI: use non-compat openat and open_by_handle_at variants

[Yury Norov]

On Thu, Aug 25, 2016 at 05:52:11PM +0200, Arnd Bergmann wrote:
> On Monday, August 15, 2016 5:30:28 PM CEST Yury Norov wrote:
> > On Mon, Jun 27, 2016 at 09:47:38AM +0200, Andreas Schwab wrote:
> > > Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx> writes:
> > > 
> > > > The only difference is that non-compat version forces O_LARGEFILE,
> > > > and it should be the default behaviour for all architectures, as
> > > > we don't support 32-bit off_t. The only exception is tile32, that
> > > > continues with compat version of syscalls.
> > > >
> > > > Signed-off-by: Yury Norov <ynorov@xxxxxxxxxxxxxxxxxx>
> > > > Acked-by: Arnd Bergmann <arnd@xxxxxxxx>
> > > > Acked-by: Chris Metcalf <cmetcalf@xxxxxxxxxx> [for tile]
> > > > ---
> > > >  arch/tile/kernel/compat.c | 3 +++
> > > >  1 file changed, 3 insertions(+)
> > > >
> > > > diff --git a/arch/tile/kernel/compat.c b/arch/tile/kernel/compat.c
> > > > index 4912084..489ae19 100644
> > > > --- a/arch/tile/kernel/compat.c
> > > > +++ b/arch/tile/kernel/compat.c
> > > > @@ -94,6 +94,9 @@ COMPAT_SYSCALL_DEFINE5(llseek, unsigned int, fd, unsigned int, offset_high,
> > > >  #define compat_sys_readahead sys32_readahead
> > > >  #define sys_llseek compat_sys_llseek
> > > >  
> > > > +#define sys_openat		compat_sys_openat
> > > > +#define sys_open_by_handle_at	compat_sys_open_by_handle_at
> > > > +
> > > >  /* Call the assembly trampolines where necessary. */
> > > >  #define compat_sys_rt_sigreturn _compat_sys_rt_sigreturn
> > > >  #define sys_clone _sys_clone
> > > 
> > > This is a no-op.  Did you mean to add this?  Without that the testsuite
> > > of tar fails on ILP32.
> > 
> > The change you suggest below is what I originally sent at the end of
> > December, but that chunk was lost after one of numerous rebases probably.
> > 
> > http://lkml.iu.edu/hypermail/linux/kernel/1512.3/00510.html
> > 
> > IIRC, the only difference between this couple of syscalls and their
> > compat versions is that non-compat syscalls set O_LARGEFILE depending
> > on (BITS_PER_LONG != 32). Next patch of this series introduces
> > ARCH_32BIT_OFF_T config option to force O_LARGEFILE for 64-bit arches,
> > and all new 32-bit arches, as ARCH_32BIT_OFF_T is enabled for existing
> > 32-bit arches explicitly.
> > 
> > O_LARGEFILE is controlled like this:
> >         -#define force_o_largefile() (BITS_PER_LONG != 32)
> >         +#define force_o_largefile() (!IS_ENABLED(CONFIG_ARCH_32BIT_OFF_T))
> > 
> > So if I restore original patch, everything will work. But my question
> > is: if ARCH_32BIT_OFF_T disables O_LARGEFILE for tile32 anyway, what
> > for we redirect native syscall handlers to compat ones? They are
> > looking identical...
> 
> I've lost context here, but let me try to recall what we had
> discussed in the past:
> 
> - native 32-bit architectures are handled using CONFIG_ARCH_32BIT_OFF_T
> - native 64-bit architectures keep setting the flag.
> - compat 32-bit architectures need special cases, but the only one
>   that exists is tile, which has to keep not setting O_LARGEFILE
>   while new compat architectures (ilp32) should set it.
>  
> > If my understanding is correct, we can drop the change in
> > arch/tile/kernel/compat.c and join this patch with next one in this
> > series.
> > 
> > Chris, Arnd?
> 
> The change in arch/tile/kernel/compat.c can either come before the
> below change, or in the same patch, but not later.
> 
> 	Arnd

Correct, I'll add it to this patch

> 
> > > diff --git a/include/uapi/asm-generic/unistd.h b/include/uapi/asm-generic/unistd.h
> > > index a26415b..4dcc38d 100644
> > > --- a/include/uapi/asm-generic/unistd.h
> > > +++ b/include/uapi/asm-generic/unistd.h
> > > @@ -178,7 +178,7 @@ __SYSCALL(__NR_fchownat, sys_fchownat)
> > >  #define __NR_fchown 55
> > >  __SYSCALL(__NR_fchown, sys_fchown)
> > >  #define __NR_openat 56
> > > -__SC_COMP(__NR_openat, sys_openat, compat_sys_openat)
> > > +__SYSCALL(__NR_openat, sys_openat)
> > >  #define __NR_close 57
> > >  __SYSCALL(__NR_close, sys_close)
> > >  #define __NR_vhangup 58
> > > @@ -676,8 +676,7 @@ __SYSCALL(__NR_fanotify_mark, sys_fanotify_mark)
> > >  #define __NR_name_to_handle_at         264
> > >  __SYSCALL(__NR_name_to_handle_at, sys_name_to_handle_at)
> > >  #define __NR_open_by_handle_at         265
> > > -__SC_COMP(__NR_open_by_handle_at, sys_open_by_handle_at, \
> > > -	  compat_sys_open_by_handle_at)
> > > +__SYSCALL(__NR_open_by_handle_at, sys_open_by_handle_at)
> > >  #define __NR_clock_adjtime 266
> > >  __SC_COMP(__NR_clock_adjtime, sys_clock_adjtime, compat_sys_clock_adjtime)
> > >  #define __NR_syncfs 267
> > 
>